---
title: Troubleshooting
description: Fixing common issues with Expo Router setup.
---

import { Terminal } from '~/ui/components/Snippet';

## Missing files or source maps in React Native DevTools

This can happen if your Chrome DevTools has exclusions within its ignore list. To fix the issue, use [React Native DevTools](https://reactnative.dev/docs/react-native-devtools):

1. Start the React Native DevTools by pressing <kbd>j</kbd> from the development server running in the terminal window
2. Open **Settings** by clicking the gear icon
3. Under **Extensions**, click **Restore defaults and reload**
4. Open **Settings** again, and go to **Ignore List** tab
5. Uncheck any exclusions for `/node_modules/`

## `EXPO_ROUTER_APP_ROOT` not defined

If `process.env.EXPO_ROUTER_APP_ROOT` is not defined you'll see the following error:

<Terminal
  cmd={[
    '$ Invalid call at line 11: process.env.EXPO_ROUTER_APP_ROOT First argument of require.context should be a string.',
  ]}
/>

This can happen when the Babel plugin `expo-router/babel` is not used in the project **babel.config.js**. You can try clearing the cache with:

<Terminal cmd={['$ npx expo start --clear']} />

Alternatively, you can circumvent this issue by creating an **index.js** file in the root of your project with the following contents:

```jsx index.js
import { registerRootComponent } from 'expo';
import { ExpoRoot } from 'expo-router';

// Must be exported or Fast Refresh won't update the context
export function App() {
  const ctx = require.context('./app');
  return <ExpoRoot context={ctx} />;
}

registerRootComponent(App);
```

Then, update your app's main entry point in **package.json**:

```json package.json
{
  "main": "index.js"
  /* @hide ... */ /* @end */
}
```

> Do not use this to change the root directory (**app**) as it won't account for usage in any other places.

## `require.context` not enabled

This can happen when using a custom version of `@expo/metro-config` that does not enable context modules. Expo Router requires the project **metro.config.js** to use `expo-router/metro` as the default configuration. Delete the **metro.config.js**, or extend `expo/metro-config`. See [Customizing metro](/guides/customizing-metro/) for more information.

## Missing back button

If you set up a modal or another screen that is expected to have a back button, then you'll need to add [`unstable_settings`](/router/advanced/router-settings/) to the route's layout to ensure the initial route is configured. Initial routes are somewhat unique to mobile apps and fit awkwardly in the system &mdash; improvements pending.

```tsx app/_layout.tsx
export const unstable_settings = {
  initialRouteName: 'index',
};
```
